Paleontologists in North Dakota have discovered a 66.5-million-year-old fossilized trackway of four giant footprints, marking the first time scientists have found connected adult Tyrannosaurus rex prints to study how the massive predator walked.
An Accidental Fossil Discovery in the Hell Creek Formation
The rare set of four connected footprints was discovered in 2025 by Kent Hups, a high school science teacher and amateur fossil hunter based in Northglenn, Colorado. Hups was volunteering on a paleontological dig led by his friend Tyler Lyson, senior curator of vertebrate paleontology at the Denver Museum of Nature & Science, when he spotted something unusual sticking out of the ground near Marmarth, North Dakota.
Working on federal land administered by the U.S. Forest Service in the badlands of southwestern North Dakota, Hups noticed a lumpy, wedge-shaped protrusion that closely resembled three splayed toes. Though Hups was convinced he had found a T. rex footprint, Lyson remained initially skeptical given how exceedingly rare adult impressions are in the fossil record.
“As a teacher, I’m always telling my students that science starts with curiosity, passion and careful observation. I never imagined that could lead me to a discovery like this.”
Kent Hups, high school teacher
When the team returned to the site the following day, they uncovered several additional footprints, revealing a continuous trail measuring roughly 23 feet long. The trackway features two left and two right footprints, each measuring about 3 feet long.
Why Adult T. rex Trackways Are Exceptionally Rare
While paleontologists have uncovered numerous skeletal remains of the apex predator in the surrounding Hell Creek Formation—which spans eastern Montana, the Dakotas, and Wyoming—fossilized footprints left by a fully grown individual have remained nearly nonexistent. Prior to this find, only two confirmed adult T. rex footprints had ever been documented globally: an isolated print found in New Mexico and another in Montana. Neither of those individual marks provided a sequence to study how the dinosaur moved.
The Hell Creek Formation itself consists of an ancient riparian habitat—a floodplain braided with streams—where soft mud typically caused footprints to erode away long before they could fossilize.
Scientists believe a unique set of environmental conditions preserved this specific stroll. Calcium carbonate and sandstone cemented into a dense, hardened mass that outlasted the surrounding mud, leaving behind raised, three-dimensional casts as the softer ground eroded away over millions of years.
High-Resolution 3D Scanning and Walking Speed Analysis
To study the weathered and fractured tracks without damaging them, the research team deployed advanced technology in the field. They used high-resolution surface scanning to digitally recreate the entire site, sending the data to Peter Falkingham, a professor of paleobiology at Liverpool John Moores University and lead author of the study published in the Journal of Vertebrate Paleontology.
Falkingham and his colleagues examined the digital models on computers and in virtual reality. Based on the spacing between each step—which spans a stride of approximately 13 feet—the researchers calculated that the animal was moving at a speed of roughly 3.4 to 4.5 miles per hour.
“The technology we’re able to apply in the digital age means my colleagues could scan the tracks in the field and then send the 3D information over to me to visualise on my computer and in VR, enabling me to take as close a look as they did in person.”
Peter Falkingham, professor of paleobiology at Liverpool John Moores University
That pace corresponds to a brisk human walking speed, suggesting the dinosaur was simply strolling across the landscape rather than sprinting when it left the impressions roughly 66.5 million years ago.
Next Steps at the Denver Museum
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